diff --git a/README.md b/README.md
index f62eae4..ba0a24c 100644
--- a/README.md
+++ b/README.md
@@ -22,6 +22,14 @@ Rename epub files to `Author - Title.epub` format using metadata from the epub f
 uv run https://tools.kzuraw.com/python/rename_epubs.py <directory> [--dry-run]
 ```
 
+### rename_invoices.py
+
+Rename invoice PDFs from `company_name invoice_number.pdf` to `yyyy-mm company_name invoice_number.pdf` format. Uses file creation date and formats the invoice number (removes whitespace, converts `/` to `-`).
+
+```bash
+uv run https://tools.kzuraw.com/python/rename_invoices.py <directory> [--dry-run]
+```
+
 ## Deployment
 
 This project is automatically deployed to Cloudflare Pages. Any changes pushed to the main branch will be reflected at [https://tools.kzuraw.com/](https://tools.kzuraw.com/).
diff --git a/python/rename_invoices.py b/python/rename_invoices.py
new file mode 100644
index 0000000..21513f8
--- /dev/null
+++ b/python/rename_invoices.py
@@ -0,0 +1,115 @@
+# /// script
+# requires-python = ">=3.14"
+# dependencies = [
+#     "click",
+# ]
+# ///
+
+"""Rename invoice PDFs to 'yyyy-mm company_name invoice_number.pdf' format."""
+
+import re
+from datetime import datetime
+from pathlib import Path
+
+import click
+
+
+def get_file_date(file_path: Path) -> tuple[int, int]:
+    """Get file creation date (year, month) from file metadata."""
+    stat = file_path.stat()
+    # Try birth time (creation time), fall back to mtime
+    timestamp = getattr(stat, "st_birthtime", None) or stat.st_mtime
+    dt = datetime.fromtimestamp(timestamp)
+    return dt.year, dt.month
+
+
+def format_invoice_number(invoice_num: str) -> str:
+    """Format invoice number: remove whitespace, convert / to -."""
+    result = re.sub(r"\s+", "", invoice_num)
+    result = result.replace("/", "-")
+    return result
+
+
+def sanitize_filename(name: str) -> str:
+    """Remove characters that are invalid in filenames."""
+    invalid_chars = '<>:"/\\|?*'
+    for char in invalid_chars:
+        name = name.replace(char, "")
+    return name.strip()
+
+
+@click.command()
+@click.argument("folder", type=click.Path(exists=True, file_okay=False, path_type=Path))
+@click.option("--dry-run", is_flag=True, help="Preview changes without renaming")
+def main(folder: Path, dry_run: bool):
+    """Rename invoice PDFs in FOLDER to 'yyyy-mm company_name invoice_number.pdf' format.
+
+    Expected input format: 'company_name invoice_number.pdf'
+    Output format: 'yyyy-mm company_name invoice_number.pdf'
+
+    The invoice number will have whitespace removed and / converted to -.
+    The date is taken from the file creation date.
+    """
+    pdfs = list(folder.glob("*.pdf"))
+
+    if not pdfs:
+        click.echo("No PDF files found.")
+        return
+
+    renamed_count = 0
+    skipped_count = 0
+
+    for pdf_path in pdfs:
+        stem = pdf_path.stem
+
+        # Skip files that already have date prefix (yyyy-mm)
+        if re.match(r"^\d{4}-\d{2}\s+", stem):
+            click.echo(f"Already has date prefix: {pdf_path.name}")
+            continue
+
+        # Parse filename: first word is company, rest is invoice number
+        parts = stem.split(maxsplit=1)
+        if len(parts) < 2:
+            click.echo(f"Skipping {pdf_path.name}: unexpected filename format")
+            skipped_count += 1
+            continue
+
+        company_name = parts[0]
+        invoice_number = format_invoice_number(parts[1])
+
+        # Get date from file creation time
+        year, month = get_file_date(pdf_path)
+
+        # Build new filename
+        new_stem = f"{year}-{month:02d} {company_name} {invoice_number}"
+        new_name = sanitize_filename(f"{new_stem}.pdf")
+        new_path = folder / new_name
+
+        if new_path == pdf_path:
+            click.echo(f"Already named correctly: {pdf_path.name}")
+            continue
+
+        if new_path.exists():
+            click.echo(f"Skipping {pdf_path.name}: target file already exists")
+            skipped_count += 1
+            continue
+
+        if dry_run:
+            click.echo(f"Would rename: {pdf_path.name} → {new_name}")
+        else:
+            pdf_path.rename(new_path)
+            click.echo(f"Renamed: {pdf_path.name} → {new_name}")
+        renamed_count += 1
+
+    if renamed_count == 0 and skipped_count == 0:
+        click.echo("\nNo files needed renaming.")
+    elif dry_run:
+        click.echo(
+            f"\nDry run complete. {renamed_count} file(s) would be renamed, {skipped_count} skipped."
+        )
+    else:
+        click.echo(f"\nRenamed {renamed_count} file(s), {skipped_count} skipped.")
+
+
+if __name__ == "__main__":
+    main()